Answer:
Biblical separation is the recognition that God has called believers out of the world and into a personal and corporate purity in the midst of sinful cultures. Biblical separation is usually considered in two areas: personal and ecclesiastical.

Personal separation involves an individual’s commitment to a godly standard of behavior. Daniel practiced personal separatism when he “resolved not to defile himself with the royal food and wine” (Daniel 1:8). His was a biblical separatism because his standard was based on God’s revelation in the Mosaic law.

A modern example of personal separation could be the decision to decline invitations to parties where alcohol is served. Such a decision might be made in order to circumvent temptation (Romans 13:14), to avoid “every kind of evil” (1 Thessalonians 5:22), or simply to be consistent with a personal conviction (Romans 14:5).

The Bible clearly teaches that the child of God is to be separate from the world. “Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness? What harmony is there between Christ and Belial? What does a believer have in common with an unbeliever? What agreement is there between the temple of God and idols? For we are the temple of the living God. As God has said: ‘I will live with them and walk among them, and I will be their God, and they will be my people.’ Therefore come out from them and be separate, says the Lord” (2 Corinthians 6:14-17; see also 1 Peter 1:14-16).

Ecclesiastical separation involves the decisions of a church concerning its ties to other organizations, based on their theology or practices. Separatism is implied in the very word “church,” which comes from the Greek word ekklesia meaning “a called-out assembly.” In Jesus’ letter to the church of Pergamum, He warned against tolerating those who taught false doctrine (Revelation 2:14-15). The church was to be separate, breaking ties with heresy. A modern example of ecclesiastical separation could be a denomination’s stance against ecumenical alliances which would unite the church with apostates.

Biblical separation does not require Christians to have no contact with unbelievers. Like Jesus, we should befriend the sinner without partaking of the sin (Luke 7:34). Paul expresses a balanced view of separatism: “I have written you in my letter not to associate with sexually immoral people—not at all meaning the people of this world who are immoral, or the greedy and swindlers, or idolaters. In that case you would have to leave this world” (1 Corinthians 5:9-10). In other words, we are in the world, but not of it.

We are to be light to the world without allowing the world to diminish our light. “You are the light of the world. A city on a hill cannot be hidden. Neither do people light a lamp and put it under a bowl. Instead they put it on its stand, and it gives light to everyone in the house. In the same way, let your light shine before men, that they may see your good deeds and praise your Father in heaven” (Matthew 5:14-16).